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From: jim@cavebear.berkeley.edu (Jim Bradley)
Newsgroups: comp.virus
Subject: can we trust diskette write-protection? (PC)
Message-ID: <0015.9104291313.AA23337@ubu.cert.sei.cmu.edu>
Date: 28 Apr 91 19:20:07 GMT
Sender: Virus Discussion List <VIRUS-L@LEHIIBM1>
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Approved: krvw@sei.cmu.edu

I am completely baffled by the following experience.

Someone sent me eight (green) 360K 5.25-inch floppy diskettes containing
pkzip archive files.

I write-protected each with a silver sticker from another box of diskettes.

I subsequently discovered that I could *freely* write or erase files from
any of these "write-protected" diskettes in the 1.2M half-height floppy drive
of an AT-clone or in the retro-fit 360K half-height floppy drive of an IBM XT.

Both machines are located in a computer lab I manage.
(I have not tested other machines,  since I am so spooked by this experience.)

When I performed the same test with the same silver stickers with the same
floppy drives,  but this time using diskettes from my own collection,
the write-protection worked correctly.

Two issues:

1) My experience (whatever the cause) suggests that write-protecting cannot
   be assumed to provide protection against virus infection if you stick
   Brand-Y diskette into Brand-X machine.

2) What is going on here?  How is it possible for a diskette drive
   to write on one brand of protected diskette, and not on another brand.
   The mind boggles.

Jim Bradley, CNR Computer Facility, UC Berkeley
jim@cavebear.berkeley.edu